Topic: Help diagnosing CB550 cylinder 4 firing

[joegeis]

Moving from my build thread here for more visibility.

I'm working on tuning the bike after a top end rebuild. The bike starts up easily when cold with choke, but will die if idle speed drops below 2k rpm, even when warm. Exhaust manifold is ~160 degrees for #1-3, but ~90 degrees on cylinder 4. I have new coils, wires, caps and plugs. Carbs were recently cleaned. Battery is 2 years old AGM, and typically on a tender.

Facts:
Battery voltage 12.9
Voltage on the blk/wht wire at the coils: 10.4
Coil primary resistance: 0.8-0.9 (with the setting on the "20")
Coil secondary resistance (no caps): 16.6 ("20k")
Cap resistance: 4.8 ("20k")

What I've done so far:
1. Disconnected my Hondaman transisitor ignition and plugged points back in to coils directly.
2. Tested for spark - I think it seems weak, but there is spark. You can see some videos I took at the bottom of the album here.

Two years ago I went through all the electrical on this bike, cleaning up and lubing connections, so although it's not perfect, the wiring should be in decent shape.

Next steps:
1. Try starting again and then check plug for wetness
2. Compression test

What else am I missing? I'm at a loss.

update -
Below is a picture of the #4 plug. It was wet when pulling it out after starting up the bike for a minute.
I also did a compression test - the first one after the top end rebuild. The engine isn't fully warm right now. I tested with both throttle closed and wide open (WFO)
#1: 120 closed 150 WFO
#2: 90 closed 138 WFO
#3: 90 closed 120 WFO
#4: 150 closed 150 WFO

So, thats really strange. I don't know if it has to do with the engine not being properly warmed up or if I didn't test it well, or if the rings are well seated yet (literally has ~30 minutes of running time since putting it back together). Maybe I'm going down the wrong rabbit hole.



Seems 1 is rich and 2-3 are lean. Doubt that has anything to do with my issue though?

[joegeis]

so I confirmed my valve clearances - all were fine.

Then I decided to check static timing with the transistorized ignition removed. I started by setting my points clearances. They were a little tight. Then I checked 1-4 side. This is where it gets fishy. The test light comes on WAY early and stays on for more than 90 degrees of the a rotation. Could this mean that I messed up reinstalling my cam chain?

Where the light comes on for 1-4:


Where the light comes on for 2-3

[grcamna2]

Too far advanced?

[bryanj]

Cam timing has nothing to do with ignition timing as advancer bolts direct to crank

[joegeis]

Too far advanced?

Yes it seems so. I have plate lined up exactly where it was before the rebuild (you can kind of see my marks in the photo), but timing as much too far advanced.

Cam timing has nothing to do with ignition timing as advancer bolts direct to crank

I don't think I have a good enough understanding here. I thought having the cam chain off by a tooth or so would affect timing, no?

I cranked the plate all the way to the right, and it moved timing closer for 1-4. I was able to get 2-3 correct with the subplate. Seems strange that it has changed so much after the rebuild. I did not replace the cam or cam chain.

Hard to see, but lines up between the T and F, to the right of both lines for 1-4:


Lines up with the T mark for 2-3

[bryanj]

Valve timing yes, ignition timing no.
On older cars the distributor is driven off the cam so cam timing off will affect ignition, on our bikes they are driven seperately

[joegeis]

Is there something else that I could have put back together wrong during the top end rebuild that would be leading to this issue? I'm not sure where to go next with the troubleshooting.

[denward17]

Assuming you are checking the ignition timing statically using a light when you say this:

"Hard to see, but lines up between the T and F, to the right of both lines for 1-4:"

Is it between the 2 lines or to the right of both lines?
If to the right, timing is advanced, use the sub plate to adjust (regardless of points gap) to the "F" mark.

You also indicate on 2-3 it lines up to T (timing) mark.  This is retarded timing.  Again, adjust sub plate to get the light on at the "F" mark.

Really not sure if this is your issue, but it wouldn't run great like this.

Edit: Do you understand which line is the T and F ?

[carnivorous chicken]

Small adjustments in the point gap can get you on those F timing marks.

But the main issue is #4 isn't firing. 1 and 4 are on the same coil and ignition point, so if 1 is firing it's not those. Have you checked the connection of the spark plug wire to the cap? If it's wet, it's not getting spark. Could also be a bad plug. Switching wire and/or plug around might expose these issues.

** Just looked at the video -- looks like there is some spark but the second video looked intermittent? Still might try switching plugs.

[joegeis]

Oh, I was mistaken. I thought I was supposed to be a TDC when static timing. This picture shows exactly where the timing light turns on for both 1-4 and 2-3.

[joegeis]

update - well, it did show where my timing was at. I decided to start over, resetting points gap, centering the plate and trying all over. I set the gap to 0.015. This time the timing is lining up at the advance marks. It feels like I'm chasing a symptom here. Something is not adding up. I've got the plate pegged all the way and its not helping. What else could be causing this issue? Are we sure the cam chain couldn't have anything to do with it?

[carnivorous chicken]

I find that closer to .012 is where the points should be, even though the range is supposed to be .012-.016. I'd start over, with the adjustment plate in the center of its range of adjustment with the point gap at .012.

[joegeis]

I find that closer to .012 is where the points should be, even though the range is supposed to be .012-.016. I'd start over, with the adjustment plate in the center of its range of adjustment with the point gap at .012.

Thanks, I'll give that a shot. Should the gap have a big impact on the timing? It's wild to me that the location that the light comes on has changed so much.

[carnivorous chicken]

Yes, the gap definitely affects timing.

[grcamna2]

update - well, it did show where my timing was at. I decided to start over, resetting points gap, centering the plate and trying all over. I set the gap to 0.015. This time the timing is lining up at the advance marks. It feels like I'm chasing a symptom here. Something is not adding up. I've got the plate pegged all the way and its not helping. What else could be causing this issue? Are we sure the cam chain couldn't have anything to do with it?

You double check your cam timing?

Was wondering how many miles on your points,or are they new?
When the rubbing blocks wear on the points,it can make it difficult to set the timing.

[jonda500]

I find that closer to .012 is where the points should be, even though the range is supposed to be .012-.016. I'd start over, with the adjustment plate in the center of its range of adjustment with the point gap at .012.

Why would you pick the smallest gap in the given range? (I have always set mine to .016")
John

[bryanj]

14 thou is the specified value with 12 to 16 being max allowables.

Changing points gap affects timing
Moving points plate WILL alter the points gap

It takes a lot of time and patience to get BOTH correct

[Little_Phil]

What you are doing is static timing. Therefore the points should open (when the points open the spark occurs) at the F line (which is to the right of the F mark and in reality quite close to the T TDC line). In reality when running the the points are only opening at around this point when on tickover and low RPMs. The advancer mechanism automatically advances the opening of the points to a point where the two further marks on the plate further CW. This can only be checked using a strobe light.
And as already said none of this can be affected by cam chain or camshaft position.

[carnivorous chicken]

I find that closer to .012 is where the points should be, even though the range is supposed to be .012-.016. I'd start over, with the adjustment plate in the center of its range of adjustment with the point gap at .012.

Why would you pick the smallest gap in the given range? (I have always set mine to .016")
John

Just found that I get my timing spot on with the smaller gap usually. But of course it takes fiddling between the plate and the points gap to get timing right. Results obviously may vary.

The OP should definitely get a strobe to time his bike though, especially to check advance...

[Deltarider]

It depends to some degree on whether you have OEM breakerpoints or aftermarket. I never had a problem with TEC breakerpoints.

[Deltarider]

Joe, I just saw your videos in the OP and I have to comment. You will not get good results with the plugs just lying on the head. The plug's contact to ground must be firm, solid, not loosely. Unless firm, the plug's hexagon's downside will arc to the head without you seeing it. As a result the spark between the plug's electrodes will be weak, if it occurs at all.
Without having read all the above, if only #4 sparkplug is not functioning right, look for possible arcing from its plugcap or -wire to the head.
addition So coil's primary resistance is 0.8-0.9 Ohm? Why? That's a coil for a CDI. Aren't you afraid you will fry them when ignition is switched on with you adjusting the timing for... how long?

[joegeis]

I have the stock points plate. The bike has about 20k miles on it. The points look in great shape to me. You can see pictures in the album I've shared. https://photos.app.goo.gl/yqMD7iLYyYHFVBuo7

I'll try going with a smaller gap, and really be meticulous about getting the static timing and the gaps as dialed in as I can.

I have a strobe light for dynamic testing, but I can't get the bike to idle below 2k rpm. I suspect cylinder 4 isn't firing correctly, which is what is throwing off my idle. I've been trying to rule out potential causes to determine why I'm having issues with the cylinder. However, maybe I'm mistaken, and its just timing is too advanced causing #4 not to combust correctly (spark before compression). I'm quite the amateur and still learning, so I could be mistaken here.

When I did my initial rebuild 2 years ago, I replaced the advance mechanism because I thought the springs were worn out and loose on my original advance and that it was causing a the engine to lazily come down in rpm after revving. The points plate is original. I still have the stock advance mechanism, so I could try throwing that back on as well.

Deltarider - thank you for the notes on testing spark! I had not considered that. After all the effort to replace and restore the ignition system, it was very disheartening to see such a weak spark! Regarding your second point, I honestly do not fully understand how the coils work and what the different resistances mean. I simply purchased the coils Hondaman recommended (PartsNmore Sakura #17-6823). I could have been testing resistance incorrectly. I've been switching the coils off as much as possible while testing timing, as I know its not good for them to be powered on without the engine running for long.

Next steps:
-Wipe the board clean on gaps and static timing. Get it juuuuust right at the .012 gap. I'll do gap, then timing, then confirm if gap changed.
-Try starting, if bike will idle at 1100-1400 rpm, set dynamic timing.
-Reinstall transistorized ignition
-profit

If I still can't get static timing right, and its still too advanced, I'll try swapping in the original advance mechanism. If that doesn't fix it, I guess I'm taking the valve cover off and checking the cam timing.

[jonda500]

As Brianj already said, the camshaft can only affect the valve timing - the points are using the crankshaft rotation to open and close them!
I was always taught to set points in the middle of the given range, but if the timing slots allow, setting the gap bigger buys you more miles before the spark quits should the points heel(cam follower) start rapidly wearing down...
John

[joegeis]

As Brianj already said, the camshaft can only affect the valve timing - the points are using the crankshaft rotation to open and close them!
I was always taught to set points in the middle of the given range, but if the timing slots allow, setting the gap bigger buys you more miles before the spark quits should the points heel(cam follower) start rapidly wearing down...
John

My understanding is the transistorized ignition system prevents the wear on the points. I need to make sure timing is right, but its not actually the points that will send the signal to the coils anymore, its the transistor.

[scottly]

The point gap needs to be set at the point with the greatest opening; sorry, but I don't recall where that is compared to the timing marks..